1. Field of the Invention
The present invention relates to an output apparatus having a plurality of character pattern generating means and, more particularly, to an output apparatus to which detachable character pattern generating means can be attached.
2. Related Background Art
Hitherto, in many output apparatuses for outputting characters of apparatuses other than a type printer as dot patterns, character code data which is given from a host computer or the like is output from a character generator by previously developing the character patterns into a frame buffer memory (image memory of one page).
The types of character pattern information which are stored into the character generator can be mainly classified into the following three fonts.
(1) A font in which a character pattern is constructed by a simple (unprocessed) dot matrix itself (hereinafter, such a font is generally referred to as a "dot matrix font")
(2) A font in which the outline and stroke of a character are stored as coordinate points for the origin of the character (hereinafter, such a font is generally referred to as a "vector font (outline font)")
(3) A font in which a dot matrix pattern is constructed in a form which was processed by using some compressing technique (for instance, run length encoding) (hereinafter, such a font is generally referred to as a "compression font")
Among those fonts, the "dot matrix font" is most frequently used in the conventional output apparatus. This is because since a character pattern itself is stored in a dot matrix, it can be easily developed into the frame buffer memory at a high speed.
However, in association with advanced functions and high resolution of the output apparatus, character processing such as rotation and deformation of characters is required. Therefore, the use of what is called a "vector font" has also generally been started. On the other hand, as a measure to the realization of a large capacity of the fonts due to the high resolution, the use of the "compression font" has been started. Further, in recent years, the hybrid type in which those three fonts are mixedly used has also been proposed. Assuming that all of those fonts are referred to as a "non-dot matrix type" for the conventional "dot matrix type", the "non-dot matrix type" fonts have an advantage which is not provided by the "dot matrix type" font. However, as compared with the general simple "dot matrix type" font, the "non-dot matrix type" fonts have a drawback such that it takes a long time to develop a character pattern into the frame buffer memory.
To solve such a drawback, many of the output apparatuses which handle the "non-dot matrix type" fonts have a memory called what is called a "font cache".
The "font cache" memory is constructed in a manner such that when the "non-dot matrix type" font is developed into the frame buffer memory, it is previously converted into the "dot matrix type" font and the pattern is stored. Such a memory is used in many output apparatuses as a method which can contribute to improve the whole processing speed.
However, the font to be previously developed into the "font cache" memory is the fixed font and there no means for changing it. Therefore, there is an inconvenience such that even if the detachable character generator (what is called a font cartridge) is attached, the ordinary font provided in the output apparatus is fixedly stored into the "font cache" memory.
The applicant of the present invention has also filed the techniques with respect to the technique (outline font) in which character data is provided as an array of coordinate points on an outline in U.S. patent application Ser. No. 854,193 filed Apr. 21, 1986, U.S. patent application Ser. No. 914,150 filed Oct. 1, 1986, U.S. patent application Ser. No. 914,733 filed Oct. 2, 1986, U.S. patent application Ser. No. 148,712 filed Jan. 26, 1988, U.S. patent application Ser. No. 151,298 filed Feb. 1, 1988, and U.S. patent application Ser. No. 156,590 filed Feb. 17, 1988. Although the above techniques are technically quite different from the present invention, they are concerned with each other with respect to the large concept such that the outline font can be handled. According to them, there are provided: the technique to independently make an outline thick or thin in the vertical and lateral directions; the technique to uniformly make an outline thick or thin; the technique to deform (shadow, hatching, or the like) an outline font; the technique to prevent the occurrence of the painting out in the process to make an outline thin; the technique to realize a corrugation of a pattern generated; the technique to correct a line width in association with the enlargement or reduction; and the like.
Although the following techniques are also technically quite different from the present invention, there have been proposed: the technique to variably magnify or paint out an outline font in U.S.P. Re No. 30,679; the technique to modify a pattern by the delay of every scanning line by a video character generator in U.S. Pat. No. 4,408,198 (Kudirka); and the like.